1. Field of the Invention
The present invention generally relates to a magnetic head inspection method and a magnetic head manufacturing method for inspecting a thin-film magnetic head, in particular, to a magnetic head inspection method and a magnetic head manufacturing method capable of inspecting a track width of a thin-film magnetic head that cannot be inspected by an optical microscope.
2. Description of Related Art
In recent years, with the rapid increase of surface recording density of the hard disk drive (HDD), the write track width of a thin-film magnetic head becomes miniaturized, and thus the importance of the technology of accurately inspecting a write track width written onto a magnetic disk by using a write pole (element) included in the thin-film magnetic head continues to increase.
In the past, an optical microscope is employed to measure the shape of the write pole (element) included in the thin-film magnetic head. However, with the miniaturization of the track width, the write track width reaches an optical system resolution limit or is narrower than the optical system resolution. Thus, it is difficult to use the optical microscope to measure the shape of the write pole (element). As a result, a scanning electron microscope (SEM) has been recently adopted to replace the optical microscope for measuring the shape of the write pole (element). However, the measurement performed by using the SEM is a kind of destructive inspection. Moreover, similar to the optical microscope, the SEM only measures the physical shape of the write pole (element), which results in the following problem. That is, it is difficult to measure the correlation with the effective magnetic track width (write track width) actually written onto the magnetic disk. In addition, even if the technology of using an atomic force microscope (AFM) to measure the shape of the write pole (element) is adopted, the same problem as described above may also exist. Recently, a magnetic head measuring device is disclosed in Japanese Patent Laid-Open Publication No. 2003-248911. The magnetic head measuring device is formed in a manner that the magnetic field characteristics, i.e., the magnetic field saturation phenomenon, of a write pole may be observed visually by using a magnetic force microscope (MFM).
When the shape of the magnetic head (write pole) is measured by using the SEM or AFM as in the past, though the physical shape of the write pole (element) can be measured, the effective magnetic track width (write track width) actually written onto the magnetic disk cannot be measured. Therefore, in the past, a head disk dedicated measuring device called a spin stand is employed to inspect the write track width in a state after the magnetic head is integrated with a suspension (i.e., a head-gimbal assembly (HGA) state) or in a simulated HGA state.
However, if the inspection with the spin stand is not performed in a final process of magnetic head manufacturing in an HGA state or a simulated HGA state, the inspection of the write track width cannot be implemented. Thus, the inspection with the spin stand is not ideal for improving the productivity or dealing with the requirement for an early feedback in the manufacturing process.
Therefore, the Applicant proposes Japanese Patent Laid-Open Publication No. 2009-230845, which disclosed a magnetic head inspection method and device disclosed in Patent Document 2. The magnetic head inspection method and device may inspect the write track width of the magnetic head in an early phase of the manufacturing process. As for the magnetic head inspection method and device, a recording signal (excitation signal) is input from a bonding pad to a thin-film magnetic head in a row-bar state, and a magnetic field generated by a write pole (element) included in the thin-film magnetic head is observed directly by using an MFM that scans and moves at a position away by a distance equivalent to a flying height of the magnetic head. In this manner, the shape of the magnetic field generated by the write pole (element) instead of the physical shape of the write pole (element) is measured; thus, a non-destructive inspection can be performed on the effective magnetic track width.
FIG. 1 is a diagram illustrating a scanning mode of the magnetic head inspection method and device disclosed in Japanese Patent Laid-Open Publication No. 2009-230845 when inspecting the effective track width of the magnetic head. When the MFM is used to scan an inspection area, the inspection area is divided into 100 lines×100 points, and the AFM is used to scan each point, so as to measure (by scanning) a surface shape (concave-convex image) of each point. The reason is that, an image filtering process is performed on a stereo surface shape of the inspection area obtained by the AFM to remove the particles, the height of a front end of a cantilever (an inspection probe) is controlled to make the front end of the cantilever at a position of a fixed height that is away from the thin-film magnetic head in the row-bar state by a distance equivalent to the flying height of the magnetic head, and meanwhile the MFM is used for scanning and observation.
However, it takes time to scan the inspection area with the AFM, and the whole tact time is hard to be reduced. In addition, the following problem also exists, that is, affected by the distance change due to the thermal drift resulting from the temperature change, or the distance change caused by the creep of an actuator of a piezoelectric element, when the MFM is used for scanning, the height of the front end of the cantilever will change.